The relationship between human cytomegalovirus and host cells will be studied in a fully permissive cell, in a partly permissive cell in which there is chronic infection, and in an abortively infected cell system. Particular attention will be apid to events that occur before viral replication, which appear to involve synthesis of an early protein. In addition, immunologic studies of human CMV will be undertaken to study strain antigenic differences and responses to early antigens. Bibliographic references: Tanaka, S., Furukawa, T., and Plotkin, S.A.; Human cytomegalovirus stimulates host cells RNA synthesis: J. Virology 15: 297-304, 1975. Furukawa, T., Tanaka, S., And Plotkin, S.A.: Stimulation of Macromolecular synthesis in guinea pig cells by human CMV Proc. Soc. Exp. Biol. & Med. 148: 211-214, 1975.